Christopher Thomas Whitlow MD,PhD, Presenter: Nothing to Disclose

Alan W Eberhardt PhD, Abstract Co-Author: Nothing to Disclose

Saami K Yazdani BS, Abstract Co-Author: Nothing to Disclose

Myles L Reedy MD, Abstract Co-Author: Nothing to Disclose

Joel L Berry PhD, Abstract Co-Author: Nothing to Disclose

Pearse Morris MD, Abstract Co-Author: Nothing to Disclose

Hip fractures and predisposing risk factors, such as osteoporosis, are generally treated with invasive surgical procedures or pharmacotherapies of varying efficacy. No minimally invasive options exist for those who fail or cannot tolerate conventional treatments. The first goal of this study was to determine if percutaneous injection of polymethylmethacrylate (PMMA) into the hip was technically possible. A second goal was to model the intervention using the computational structural method of finite element analysis (FEA) to determine if infused PMMA decreases femoral neck stress.

Fresh human cadaveric pelvises (N = 4) were placed in a prone orientation. Biplane fluoroscopy was directed to guide an 11-gauge needle into the neck of the femur, and a column of PMMA injected. Pre- and post-procedure CT data were obtained and reconstructed into a 3-D model to evaluate the injection technique and perform FEA. FEA is performed by dividing a 3-D graphic object into smaller elements. These elements are assigned mechanical properties and loads via precise equations that are solved for resultant deformation and stress. In the present study, densitometric CT data were used to generate elasticity parameters that characterize mechanical properties of the femoral neck. FEA was then used to calculate properties of elements in the model under specific loading conditions before and after PMMA injection. The engineering failure criterion of von Mises stress was used to evaluate the femoral neck after loading in one-legged stance.

CT and fluoroscopy images demonstrate that PMMA can be injected percutaneously as a column running through the neck of the femur. FEA reveals a 20% reduction in the average von Mises stress around the femoral neck after PMMA injection.

PMMA can be consistently placed into the hip where fractures occur, and it effectively decreases stress in cortical bone of the femoral neck, possibly reducing fracture risk. Optimization of PMMA delivery and the PMMA-bone interface may reveal further mechanical advantages that reduce fracture risk. PMMA injection into hip, therefore, may provide a viable prophylactic treatment for individuals at imminent risk for hip fracture.

P.M.: Parallax Medical Inc. Research Grant

Whitlow, C, Eberhardt, A, Yazdani, S, Reedy, M, Berry, J, Morris, P, Fluoroscopy-guided Percutaneous Injection of Polymethylmethacrylate into Cadaveric Hip: A Possible Prophylactic Treatment for Individuals at Risk for Hip Fracture.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4406389.html